Electrochemical sensing based on nanopatterned functional surfaces

Abstract

An approach to creating microelectronic circuitry that relies on selfassembly of polymer materials can be used as a general technique for surface nanoengineering a host of different material types.'Bottom-up,' 'chemical nanopatterning,' and 'nanophase separation' are all common expressions that describe potential techniques for nanoengineering surfaces and substrates without recourse to physical methods such as lithography. The hope of being able to create surface arrangements of precise periodicity and dimension has been around since the original papers on selfassembly (and the quite distinct concept of self-organization). These efforts reported how molecular and physical entities can spontaneously organize themselves into regular arrangements through intermolecular forces. 1 Despite the promise of this approach, there are relatively few examples where self-assembly has had a real impact in a commercial sense. One clear success is so-called mesoporous materials, which are manufactured for chromatography and sorption applications. 2 Self-assembly has been most closely associated with nanotechnology and the development of nanosized electronic devices. But here, too, apart from some demonstrators, the goal of having arrays of devices formed by self-assembly has yet to be achieved. 3 One form of self-assembly, however, is moving toward device manufacture. Block copolymer (BCP) lithography is becoming a viable, scalable, and realizable method for line space (interconnects, devices) and hole (via) patterning at ultrasmall feature sizes. 4, 5 Here, using techniques such as grapho-and chemo-epitaxy, the microphase separation of BCPs can achieve extremely ordered arrangements through chemical interactions between the constituent polymer blocks. The polymer patterns can be integrated into current fabrication schemes as a non-UV lithographic on-chip etch mask provided one block in the pattern can be selectively removed. Figure 1 shows brief examples of the progress in this area. Figure 1. Typical block copolymer (BCP) patterns formed in topographically patterned surfaces. (A) and (B) represent vertical and parallel orientation of hexagonal-cylinder-forming polystyrene-b-polydimethylsiloxane. (C) and (D) represent silicon structures formed by pattern transfer of similar arrangements to (B). (With permission of author and M. Zelsmann,The work in BCP nanolithography has been driven by the challenges-financial and technical-in providing sub-8nm resolution in transistor circuitry and has dominated academic and industrial research in this area. 5 However, we have learned a great deal about how these patterns can be achieved, morphology and structural control, as well as choices of polymers, and how a range of materials can be realized. 4, 5 Outside microelectronics, where the need for precise positioning and dimensional regularity is somewhat reduced, the application of BCPs in fields that require patterning of sub-50nm feature size has been somewhat neglected despite their low cost. Indeed, the challenges in terms of their comm...